Louie's family always supports him, from the time he's a trouble teenager, to when he's a track superstar, and, finally when he's a decorated war hero. His father, Anthony, was a coal miner, boxer, and construction worker, and his mom, Louise, is a housewife who had Louie when she was eighteen. They do not come from illustrious beginnings, and the Zamperinis lived in a one-room shack for a year—with no running water—that Louise defended with a rolling pin.
That's just one of the ways we're shown that Louise is crafty and scrappy, just like her son. She even gets into a fight with four kids who try to steal her pants and later bribes one of Louie's schoolmates to spy on him. In other words, this mom wouldn't seem out of place in your average network primetime sitcom.
Throughout Unbroken, we get glimpses of what the Zamperinis are up to while Louie is lost at sea and imprisoned. They too are unbroken, never losing faith that their son is still alive. Even though Louise develops a rash when she learns of Louie's disappearance, she never believes that her son is dead. Sylvia, Louie's sister, takes his disappearance hard too—she is often "wracked with anxiety" and "barely able to eat" (4.21.9), but she also believes in her brother's strength and ingenuity.
Louie loves his whole family, but he is perhaps closest to his brother, Pete. Pete is "everything [Louie] was not" (1.1.23) when the boys are younger, and it's Pete's strong influence that changes Louie's life. Pete convinces Louie to try his hand (well, his feet) at athletics, and he always believes in his brother, even trying to get him to break the four-minute mile.
If Louie didn't have such a strong family unit, we wouldn't have Unbroken. Laura Hillenbrand seems to have relied just as much on their memories and mementos (like Pete's giant Louie-related scrapbook) to weave together Louie's tale, so not only do they hold Louie up throughout his life, but they also help make this book possible.